1. Technical Field
The present invention relates to a print system, such as an ink jet printer, which performs printing on a medium, such as a sheet that is transported.
2. Related Art
In the related art, as an example of a print apparatus, an image forming apparatus that records (prints) an image on a sheet (medium) that is transported is known. In addition, there is an image forming apparatus including a switchback mechanism (inversion unit) that inverts the sheet in the image forming apparatus (for example, JP-A-9-12198).
That is, the switchback mechanism includes a roller, and a sheet fed from an upstream side transport path (first transport path) is sent and inverted on a downstream side transport path (second transport path) by rotating and counter-rotating the roller.
In the image forming apparatus, two switchback mechanisms are provided; one roller is used as a roller that feeds the sheet to one switchback mechanism and another roller is used as a roller that sends the sheet from the other switchback mechanism. That is, when the roller rotates, the sheet is fed to the one switchback mechanism and the sheet is sent from the other switchback mechanism. When the roller counter-rotates, the sheet is sent from the one switchback mechanism and the sheet is fed to the other switchback mechanism.
Therefore, the roller sends the sheet from the switchback mechanism to the downstream side transport path at the same speed as a speed for feeding the sheet from the upstream side transport path to the switchback mechanism.
However, for example, when printing is performed by adhering liquid such as ink to a surface of a sheet, there is a case where curling of the sheet such as curving of the sheet occurs. Curling is considered to occur due to a difference in the expansion rates between a swollen portion of a front surface permeated by the adhered liquid and a rear surface not permeated by the liquid such as the ink. The curling due to the liquid permeating a rear surface or the liquid evaporating gradually decreases over time following the adhering of the liquid to the sheet.
In addition, the shape of the sheet caused to swell by absorbing the liquid is fixed in accordance with the evaporation and drying of the liquid. That is, for example, when the sheet dries while transport of the sheet is stopped, the sheet is fixed in the shape of a transport path. Therefore, it is preferable that the shape be changed by transporting the sheet until the adhered liquid dries.
In the case of the image forming apparatus of JP-A-9-12198, the speed for sending the sheet from the switchback mechanism is determined in accordance with the speed for feeding the sheet to the switchback mechanism. Therefore, there is a problem that the transport path of the sheet is increased to increase the transport time such that the size of the apparatus increases.
The problem is not limited to the image forming apparatus that performs recording on a sheet, but is common to print apparatuses that print on a medium.